The present invention relates, in general, to closure systems for molded plastic containers. In particular, the present invention relates to closure systems for molded plastic containers containing sterile fluids and having a cap associated therewith.
Various food, medical and household products are presently packaged in molded plastic containers. Most of these containers include a dispensing port, and a closure system which creates a barrier for containing and/or protecting the contents of the container until the contents are to be used. Presently, many of these closure systems employ caps which are adapted to be easily removed. In particular, molded plastic containers are used to dispense sterile medical fluids for use in various medical procedures. For example, intravenous solution containers are used to administer parenteral solutions to a patient. Other medical containers are used to dispense irrigating fluids to a surgical site. Still other medical containers are used in enteral nutrition, inhalation, nebulizer, orthoscopic, mirror defogging, and x-ray preparation applications.
These medical containers have a common purpose of maintaining the sterility of their contents during manufacture, shipping, storage and dispensing. A critical portion of these containers is the closure system. The closure system must form and maintain a sterile barrier at a cap/container interface. This sterile barrier must remain intact from the time it is established until the time the container is intentionally opened for use. At the same time, these containers must be easily opened so that the contents of the container may be dispensed at the time of use.
The manufacture of medical containers typically includes a sterilization process such as autoclaving which subjects the container and contents to high temperatures typically in the range of approximately 118-121 degrees C. These temperatures can cause the pressure inside the container to be elevated above the pressure existing outside the container. Also, as the container is being cooled down from sterilizing temperatures, the pressure inside the container may drop below the pressure existing outside the container. The sterile barrier must be capable of withstanding these pressure differentials, to prevent air from any non-sterile environment which may exist outside the container from being drawn into the container during these processes, in order to maintain the sterile barrier.
As the contents of a container are being dispensed, the contents may come into contact with portions of the exterior of the container, therefore, it is often desirable that these areas also remain sterile. For this reason, the sterile barrier is typically located such that an exterior portion of the container adjacent to the dispensing port, including any threadings on the exterior of the container neck, is positioned between the sterile barrier and the contents of the container. In this way, the sterility of an external portion of the container can be maintained.
One means of providing a sterile barrier at a cap/container interface is to place a resilient gasket between the cap and the container and to exert compressive forces to sandwich together the cap, gasket and container whereby a sterile barrier may be established. Nevertheless, continuing problems remain in such closure systems in preventing the breach of the sterile barrier. Inherent factors can create difficulties in the establishment, maintenance and reliability of the sterile barrier. For example, typically the gasket is a separate component of the closure system, which requires that two critical sterile barriers be established and maintained; one at a cap/gasket interface and a second at a gasket/container interface. The reliability of such closure systems, which are dependent on the maintenance of two critical sterile barriers, is lessened as both sterile barriers are subject to failure. Also, such closure systems typically are not constructed to minimize movement and/or expansion of a gasket in directions other than the directions of applied compressive forces. This can affect the integrity and the reliability of such a closure system. Also, dimensional variations due to molding tolerances of cap, container and gasket components can make such closure systems unreliable and prone to failure.
Therefore, it is desirable to provide a closure system which forms a sterile barrier having high integrity and operational reliability. It is desirable that the sterile barrier be located so that an external area adjacent to the dispensing port remains sterile. It is also desirable to provide a closure system which allows the container to be easily opened so that the contents of the container may be dispensed at the time of use. Furthermore, since closure systems are often used only once and are disposed of after use, it is desirable that the cost of manufacturing the closure system is relatively low.
In accordance with the present invention there is provided a closure system for molded plastic containers which is capable of providing a sterile barrier or seal having high integrity and operational reliability. Also, the present invention provides a sterile barrier which is located so that the sterility of an external area adjacent to the dispensing port can be maintained in a sterile condition. Also, the present invention provides a closure system which allows the container to be easily opened at the time of use and which can be manufactured economically.
Specifically, the closure system comprises a screw cap having internal threading constructed for engagement with threading located on the exterior of the container neck. The cap has a sidewall. Inner and outer annular rims are integrally formed and extend downwardly from the sidewall of the cap. A resilient compressible gasket is positioned between the annular rims. The gasket is designed to engage against an abutment surface integrally formed in and extending radially from the container neck, to establish a sterile barrier when the cap is rotated downwardly onto the container neck.
In a preferred embodiment, the gasket and cap are integrally formed in a single injection molding operation to create a unitary component. Also, the abutment surface is subjected to an ultrasonic treatment, called swaging, which smooths the molding seams created during the molding process, particularly along the points-of-contact made by the gasket with the abutment surface when the gasket is fully seated against the abutment surface.
Thus, in accordance with the present invention, a closure system is provided which forms a sterile barrier having high integrity and operational reliability, is easily opened at the time of use, and has a relatively low manufacturing cost.
Numerous other advantages and features of the present invention will become readily apparent from the following detailed description of the invention and the disclosed embodiments thereof, from the claims and from the accompanying drawings in which the details of the invention are fully and completely disclosed as part of this specification.